Thermal vacancies in random alloys in the single-site mean-field approximation

TL;DR

This paper develops a formalism to calculate vacancy formation energies in random alloys using a single-site mean-field approximation, highlighting how configurational entropy affects vacancy concentrations at high temperatures.

Contribution

It introduces a formalism for vacancy energetics in random alloys within the single-site mean-field approximation, accounting for configurational entropy effects.

Findings

Vacancy concentration decreases at high temperatures due to configurational entropy.

Effective vacancy formation energy increases with temperature but remains below the homogeneous model value.

Numerical example with Cu-Ni alloy illustrates the formalism's application.

Abstract

A formalism for the vacancy formation energies in random alloys within the single-site mean-filed approximation, where vacancy-vacancy interaction is neglected, is outlined. It is shown that the alloy configurational entropy can substantially reduce the concentration of vacancies at high temperatures. The energetics of vacancies in random Cu-0.5Ni-0.5 alloy is considered as a numerical example illustrating the developed formalism. It is shown that the effective formation energy is increases with temperature, however, in this particular system it is still below the mean value of the vacancy formation energy which would correspond to the vacancy formation energy in a homogeneous model of a random alloy, such as given by the coherent potential approximation.